1) Field of the Invention
A method for reducing outside air inflow required for aircraft cabin air quality is provided. More particularly, a method for reducing outside air inflow required for aircraft cabin air quality based on aircraft operating parameters is provided.
2) Description of Related Art
Known commercial and military aircraft supply either a fixed or variable outside air inflow based on satisfying a plurality of requirements, one of which, passenger cabin air quality, is directly affected by leakage of air from within the aircraft pressurized volume to the ambient environment, commonly referred to as fuselage leakage. Traditionally, the fuselage leakage has been assumed a conservatively high constant value associated with an older aircraft. Therefore, the outside air inflow required for passenger cabin air quality can be significantly less for a newer aircraft with lower fuselage leakage. This traditional fuselage leakage assumption can reduce aircraft efficiency. Conversely, the outside air inflow required for passenger cabin air quality can be significantly greater for an aircraft with higher fuselage leakage. In this case, the traditionally assumed fuselage leakage value will degrade passenger cabin air quality. In addition, there are no feedback or alert methods to flight crews regarding aircraft fuselage leakage until the aircraft pressurized volume pressure setpoint can no longer be maintained.
Devices that pressurize and transport outside air into the aircraft pressurized volume consume energy proportional to the outside air inflow rate and differential pressure between the ambient environment and the pressurized volume which includes the passenger cabin. When the driving outside air inflow requirement is passenger cabin air quality, i.e., when the ventilation, temperature control, smoke penetration from one compartment to another, displacement of contaminated air, repressurization, and all other outside air inflow requirements are numerically lower, a reduction in fuselage leakage decreases the passenger cabin air quality outside air inflow requirement. This allows the aircraft to be operated with less outside air inflow and greater energy efficiency. Aircraft fuselage leakage increases with vehicle age, primarily due to an increase in door seal leakage. Maintenance of door seals is usually performed following flight crew observation of cabin pressure problems, such as an inability of the aircraft to meet its pressurized volume pressure setpoint, or due to increased passenger cabin noise level. Outside air inflow requirements for passenger cabin air quality typically assume a conservatively high fuselage leakage value. Therefore, every flight hour when the actual fuselage leakage value is numerically lower and passenger cabin air quality is the driving outside air inflow requirement, unnecessary outside air is pressurized, transported from the ambient environment into the fuselage and discharged overboard. Accordingly, there is a need for a method for reducing outside air inflow required for aircraft passenger cabin air quality that does not have the problems associated with known methods.